1. Field of the Invention
The present invention relates generally to a resinous member with characters, letters, figures, etc., visually arranged therein, and more particularly to a key top member, comprising a resinous member, of a key used in a keyboard as a data input device of an electronic machine.
2. Description of the Related Art
Demands for the multi-function or flexibility of electronic machines causes various requirements for keyboards of the electronic machines, such as an improvement in the visibility of characters provided on the surface of a key. Especially, in portable electronic machines, it is desired to more easily operate the key even in a dark place.
Conventionally, various methods have been used to provide the characters, etc. on the surface of a key top member of the key, such as a two-color molding process, or a sublimation, a pad printing or a laser beam machining on the surface of a resinous member. These methods have been selectively used in accordance with a cost requirement, a manufacturing scale, an application purpose, or the like. Also, attempts have been made in these methods to improve the visibility of the key top member or of the characters provided on the key top member.
Japanese Unexamined Patent Publication (Kokai) No. 8-174716 (JPP'716) discloses a key top member of a key used in a keyboard, which can improve the visibility of a character. As shown in FIG. 1A, the key top member 1 includes a resinous molded part 2 with a top surface 3 slanted by an angle .theta., a sheet 4 mounted on the top surface 3, a character 5 printed on the sheet 4, and a transparent resinous molded piece 6 formed on the top surface 3 to cover the sheet 4. A contact part 7 is formed on a bottom surface of the key top member 1 to bring conductors (not shown) into contact with each other. A skirt 8 is elastically deformed by pushing down the key top member 1. The slanted top surface 3 of the resinous molded part 2 can improve the visibility of the character 5 upon being looked at from the front side of the keyboard.
JPP'716 also discloses another key top member which can improve the visibility of a character. As shown in FIG. 1B, the key top member 1 includes a resinous molded part 9 with a top surface 3 slanted by an angle .theta., which is made of a material causing a color development by a laser beam irradiation, and a transparent resinous molded piece 6 formed on the top surface 3 and having a top surface generally parallel to the top surface 3. After molding the transparent piece 6 on the molded part 9, a laser beam is irradiated on the top surface 3 to cause a color development of a coloring matter contained in the material of the molded part 9 and to form a character 10. This key top member 1 can also improve the visibility of the character 10 upon being looked at from the front side of the keyboard.
Japanese Unexamined Utility Model Publication (Kokai) No. 3-57831 (JUMP'831) discloses a key top member of a push-button switch mechanism, which can improve the visibility of a key top member in a dark place. As shown in FIG. 1C, a key top member 1, a light source 11, a light guide member 12 and a switch 17 are accommodated in a casing 18. The key top member 1 is provided with a light guide part 13, a peripheral shading part 14, a top phosphor part 15 and a bottom light reflecting surface 16. Light "L" emitted from the light source 11 passes through the light guide member 12 and enters into the light guide part 13. Then, the light "L" is reflected by the light reflecting surface 16 and irradiates the phosphor part 15. The light source 11 intermittently emits light, and the afterglow of the phosphor part 15 is used to visually observe the key top member 1.
Japanese Unexamined Patent Publication (Kokai) No. 5-314855 (JPP'855) also discloses a key top member of a push-button switch mechanism, which can improve the visibility of a key top member in a dark place. As shown in FIG. 1D, a key top member 1 made of a light guide material 19 is mounted in a hole of a casing 18, and a phosphor part 15 is provided on the upper surface of the casing 18 to surround the hole. Light "L" emitted from a light source 11 passes through the light guide member 20 and enters into the light guide material 19. Then, the light "L" is emitted from the key top member 1 and thus the key top member 1 can be visually observed. A part of the light "L" emitted from the key top member 1 and an external light (not shown) irradiate the phosphor part 15 and are stored in the latter. When the light source 11 does not emit light, the key top member 1 is illuminated by the afterglow of the phosphor part 15, and can be visually observed in a dark place.
In another technical field, different from the field of the above key top members, it is well known that a resinous member, such as a package of an electronic part, is provided with characters for representing, e.g., a rating. Such characters to be provided on the package are also formed by irradiating the resinous member with a laser beam, because of the easy formation of the characters.
Japanese Unexamined Patent Publication (Kokai) No. 4-38857 (JPP'857) discloses a package of a semiconductor. As shown in FIG. 2A, a black resinous molded package 21 accommodating a semiconductor (not shown) having leads 22 is provided with grooves 23 for representing characters. The grooves 23 are formed by irradiating the top surface of the package 21 with a laser beam. To improve the visibility of the characters, the surface of the black package 21 is covered by an yellow resinous layer 24, as shown in FIG. 2B. When the yellow layer 24 is cut out or engraved by a laser beam, the black package 21 is exposed at cut-out portions 25, and thus black characters are formed on an yellow ground, whereby the excellent visibility of the characters can be obtained.
Japanese Unexamined Patent Publication (Kokai) No. 4-116955 (JPP'955) also discloses a package of a semiconductor. As shown in FIG. 2C, a resinous molded package 21 accommodating a semiconductor (not shown) having leads 22 is provided on the top surface of the package with grooves for representing characters, and is covered on the top surface by a transparent resinous coating 26. When a vacuum nozzle (not shown) used for mounting the package 21 onto a circuit board, the grooves formed by a laser beam on the top surface of the package 21 tend to make a gap between the top surface and the vacuum nozzle to reduce a suction force of the vacuum nozzle. The coating 26 acts to eliminate this problem.
Japanese Unexamined Patent Publication (Kokai) No. 5-16581 (JPP'581) discloses a method for providing characters on the surface of a card. The card includes a protective layer 27a and a magnetic recording layer 27e. Between these layers 27a and 27e, some layers 27b to 27d made of resin or metal having different colors are arranged. The laminated structure thus formed is provided with grooves 28a to 28c with different depths, formed by irradiating the laminated structure with differently powered laser beam. Thus the bottoms of the grooves 28a to 28c respectively leach differently colored layers 27b to 27d, and thereby the visibility of the characters represented by the grooves 28a-28c is improved.
The above-mentioned conventional techniques, for improving the visibility of the characters formed on a resinous molded member by a laser beam machining, have certain problems. For example, in the techniques disclosed in JPP'857 and JPP'581, the visibility of the characters is improved by irradiating a laminated structure having differently colored laminations with differently powered laser beam to form differently colored characters. However, these techniques have a common problem that a manufacturing cost is increased. Also, the technique, as disclosed in JPP'716, for causing a color development of a coloring matter contained in the material of a pale-colored resinous molded member by a laser beam irradiation, or for coloring the surface of the resinous molded member by darkening or carbonizing the material thereof, relatively simply forms a character. However, in this technique, the density of the character is insufficient, and thus it has been required to improve the visibility of the colored character.
On the other hand, the above-mentioned conventional techniques, for improving the visibility of the characters formed on a key top member in a dark place, have also certain problems. For example, in the techniques disclosed in JUMP'831 and JPP'855, the visibility of the characters in a dark place is improved by irradiating a key top member and a phosphor part with light emitted by a light source. However, these techniques have common problems, in portable use, in that the number of components is increased due to the light source, etc., and that electric power is consumed for illuminating the light source. Thus, it has been required to improve the visibility of the character formed on the key top member in a dark place, without using any electrically powered light source for illuminating the key top member.